updated GitHub action's runner OS (#95)

* updated python v to 3.6.8

* fix version with wildcard

* Update python-package.yml

* removed py 3.6 from workflow test

* updated runner OS and added py36

.github/workflows/python-package.yml

@@ -1,5 +1,5 @@
 # This workflow will install Python dependencies, run tests and lint with a variety of Python versions
-# For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions
+# For more information see:https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-python#using-multiple-python-versions
 
 name: Python package
 
@@ -12,15 +12,15 @@ on:
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9.1]
+        python-version: ["3.6", "3.7", "3.8", "3.9"]
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v2
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies